CN111128419A - Nuclear power plant fuel assembly integrity judgment method - Google Patents
Nuclear power plant fuel assembly integrity judgment method Download PDFInfo
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- CN111128419A CN111128419A CN201911396837.1A CN201911396837A CN111128419A CN 111128419 A CN111128419 A CN 111128419A CN 201911396837 A CN201911396837 A CN 201911396837A CN 111128419 A CN111128419 A CN 111128419A
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- fuel assembly
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
- G21C17/07—Leak testing
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/02—Devices or arrangements for monitoring coolant or moderator
- G21C17/04—Detecting burst slugs
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention belongs to the technical field of nuclear reactor radiochemistry, and particularly relates to a nuclear power plant fuel assembly integrity judgment method. Sampling the main coolant system to analyze gamma nuclide concentration data, including Xe-133, Xe-135; dividing the analyzed Xe-133 concentration data by the Xe-135 concentration data to obtain a ratio; the ratio of Xe-133 to Xe-135 in all the main coolant sampling analysis data in the reactor operating period is arranged in ascending order from small to large; performing linear fitting on the data after the ascending sequence arrangement to obtain a fitting linear formula and a linear slope of the fitting linear formula; when the ratio of Xe-133/Xe-135 fits a straight line with a slope >0.01, breakage of the fuel assembly occurs; when the Xe-133/Xe-135 ratio fits a straight line with a slope <0.005, no breakage of the fuel assembly occurs. The method can quickly and accurately judge whether the fuel assembly is damaged.
Description
Technical Field
The invention belongs to the technical field of nuclear reactor radiochemistry, and particularly relates to a nuclear power plant fuel assembly integrity judgment method.
Background
It is a common occurrence of pressurized water reactor nuclear power plant fuel assemblies breakage during operation. Currently, each nuclear power plant is mainly based on processing the radioactive concentration data of gamma nuclide by sampling and analyzing a primary coolant and carrying out fuel assembly integrity judgment during the operation of the reactor by combining the operation state of a sampling time group.
1. Fission product release mechanism
During normal reactor operation, when the fuel rod cladding is breached, coolant can enter the fuel through the cladding gap and fission products (such as highly volatile inert gases and radioactive iodine) will be released into the primary system coolant, causing a sudden increase in the radioactivity level of the primary system coolant. Fission product release may be exacerbated as the coolant passes through the fuel cladding breach due to the primary system coolant operating pressure being higher than the fuel rod internal gas pressure.
Radioactive iodine release may also occur during reactor shut-down or power changes. When the temperature within the fuel rod is reduced below saturation through cladding cracking, the liquid water in the primary system coolant will dissolve soluble iodine in the fuel cladding cracks, resulting in an "iodine spike" phenomenon. Thereafter, water from the primary system coolant, which is rich in radioactive iodine, will continue to remain in the fuel clad crevices and will be released during subsequent reactor startup.
2. Common method for fuel assembly breakage
The earliest indication of fuel assembly failure is an abnormally high Xe-133 activity. The radioactive iodine activity change is less correlated when the fuel assembly is initially broken, because a small breach or crack in the fuel cladding does not result in a measurable change in iodine concentration at the unit steady state. The "iodine peak" accompanying the power transient is generally considered by the nuclear power plant as a reliable indicator of the occurrence of the fuel assembly breakage, and is also a common method for determining whether the fuel assembly breakage occurs in the nuclear power plant.
3. Power transient presence or absence of iodine peak
A fuel assembly of a certain nuclear power plant 101, 201, 301, 302, 401 for five operating cycles is damaged and a distinct iodine peak is found in the power transient. The 202 cycle fuel assembly had visible breaches, but no significant iodine peak was found at the power transient. Thus, as long as the power transient has an iodine spike, it can be considered that a fuel assembly is broken; the power transient state has no iodine peak, the fuel assembly is not necessarily not damaged, and other parameters are combined for assisting judgment. The method for determining whether a fuel assembly commonly used in a power plant is damaged has certain defects.
Disclosure of Invention
The invention aims to provide a method for judging the integrity of a fuel assembly of a nuclear power plant, which can accurately judge the integrity of the fuel assembly in time during the normal operation of a reactor and make up for the defects of the traditional method for judging the damage of the fuel assembly.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a nuclear power plant fuel assembly integrity determination method samples a primary coolant system for analysis of gamma nuclide concentration data, including Xe-133, Xe-135; dividing the analyzed Xe-133 concentration data by the Xe-135 concentration data to obtain a ratio; the ratio of Xe-133 to Xe-135 in all the main coolant sampling analysis data in the reactor operating period is arranged in ascending order from small to large; performing linear fitting on the data after the ascending sequence arrangement to obtain a fitting linear formula and a linear slope of the fitting linear formula; when the ratio of Xe-133/Xe-135 fits a straight line with a slope >0.01, breakage of the fuel assembly occurs; when the Xe-133/Xe-135 ratio fits a straight line with a slope <0.005, no breakage of the fuel assembly occurs.
The beneficial effects obtained by the invention are as follows:
the method can quickly and accurately judge whether the fuel assembly is damaged. The method is used for independently judging the integrity of fuel assemblies of partial nuclear power plants in China, and the judgment result is consistent with the conclusion of the integrity of the fuel assemblies finally given by each power plant; the present method determines fuel assembly integrity conditions that cannot be determined using conventional methods and can lead to fuel assembly integrity conclusions earlier than conventional methods. The slope of a straight line fitted by a ratio Xe-133/Xe-135 of a broken fuel cycle in part of domestic nuclear power plants.
When the U2C2 circulating fuel assembly of the domestic A nuclear power plant is found to be damaged during the appearance inspection of the fuel assembly during the overhaul of the unit, but according to the traditional fuel assembly integrity judgment method, because no obvious iodine peak exists, the conclusion whether the fuel assembly is damaged cannot be given. The slope of a fitted straight line of the ratio of Xe-133 to Xe-135 obtained by the method is 0.0106, meets the condition of breakage of the fuel assembly given by the method, and judges that the fuel assembly is broken.
When the data of the inert gas of the main coolant circulated by the U3C3 nuclear power plant A in China is abnormal, the radioactive iodine equivalent does not have an obvious iodine peak when the power of the unit is transient, and whether a fuel assembly is damaged or not can not be judged by using a traditional method. The slope of a fitted straight line of the Xe-133/Xe-135 ratio obtained by using the method is 0.0402, and the broken fuel assembly is judged according to the condition that the fuel assembly is broken given by the method. The cycle also showed a more pronounced iodine peak at month 4 after the conclusion of fuel assembly failure was made by the present method, which also concluded that fuel assembly failure occurred using conventional methods.
In the domestic F nuclear power plant U4C3 fuel circulation, partial inert gas data are abnormal in the down-going stage of unit overhaul, but no iodine peak appears. With the conventional method, it is impossible to determine whether the fuel assembly is broken. The slope of a fitted straight line of the Xe-133/Xe-135 ratio obtained by the method is 13.42, meets the condition that the fuel assembly is damaged given by the method, and judges that the fuel assembly is damaged.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The integrity judgment method for the nuclear power plant fuel assembly comprises the following steps:
the main coolant system is sampled to analyze gamma species concentration data, including Xe-133, Xe-135. The analyzed Xe-133 concentration data is divided by the Xe-135 concentration data to obtain a ratio. The Xe-133 and Xe-135 ratios in all the primary coolant sampling analysis data over the reactor operating period are ordered in ascending order from small to large. And performing linear fitting on the data after the ascending sequence arrangement to obtain a fitting linear formula and a linear slope of the fitting linear formula. When the ratio of Xe-133/Xe-135 fits a straight line with a slope >0.01, breakage of the fuel assembly occurs; when the Xe-133/Xe-135 ratio fits a straight line with a slope <0.005, no breakage of the fuel assembly occurs.
Claims (1)
1. A nuclear power plant fuel assembly integrity determination method is characterized by comprising the following steps: sampling the main coolant system to analyze gamma nuclide concentration data, including Xe-133, Xe-135; dividing the analyzed Xe-133 concentration data by the Xe-135 concentration data to obtain a ratio; the ratio of Xe-133 to Xe-135 in all the main coolant sampling analysis data in the reactor operating period is arranged in ascending order from small to large; performing linear fitting on the data after the ascending sequence arrangement to obtain a fitting linear formula and a linear slope of the fitting linear formula; when the ratio of Xe-133/Xe-135 fits a straight line with a slope >0.01, breakage of the fuel assembly occurs; when the Xe-133/Xe-135 ratio fits a straight line with a slope <0.005, no breakage of the fuel assembly occurs.
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| CN201911396837.1A CN111128419B (en) | 2019-12-30 | 2019-12-30 | Nuclear power plant fuel assembly integrity judgment method |
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| CN201911396837.1A CN111128419B (en) | 2019-12-30 | 2019-12-30 | Nuclear power plant fuel assembly integrity judgment method |
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| CN111128419A true CN111128419A (en) | 2020-05-08 |
| CN111128419B CN111128419B (en) | 2023-01-24 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113571213A (en) * | 2021-06-23 | 2021-10-29 | 中国原子能科学研究院 | Method for detecting integrity of neptunium target in irradiation process |
| CN113782238A (en) * | 2020-06-09 | 2021-12-10 | 中核武汉核电运行技术股份有限公司 | Method for identifying fuel assembly damage by on-line sipping |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113782238A (en) * | 2020-06-09 | 2021-12-10 | 中核武汉核电运行技术股份有限公司 | Method for identifying fuel assembly damage by on-line sipping |
| CN113571213A (en) * | 2021-06-23 | 2021-10-29 | 中国原子能科学研究院 | Method for detecting integrity of neptunium target in irradiation process |
| CN113571213B (en) * | 2021-06-23 | 2024-03-22 | 中国原子能科学研究院 | Method for detecting neptunium target integrity in irradiation process |
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| CN111128419B (en) | 2023-01-24 |
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